The present invention relates to a tube bending machine comprising a bending head and an automatic loading system arranged to load a tube to be bent on the bending head. According to a further aspect, the present invention relates to a method for automatic loading of tubes on the bending head of a tube bending machine.
The term “tube” used in the following description and claims is to be intended as referring also to any other elongated blank, such as a bar or a profiled section. Likewise, the term “tube bending machine” is to be intended as referring also to a machine arranged to bend any other elongated blank, such as a bar or a profiled section.
Different kinds of automatic loading systems for tube bending machines are available on the market and in their simplest and cheapest form basically consist of an inclined plane on which the tube to be bent is caused to slide, the inclined plane being provided with stop members to stop the tube to be bent. The tube bending machines provided with such automatic loading systems are able to take a tube positioned on the inclined plane and to put down the worked tube on the ground by suitable control of the machine axes. In these tube bending machines, the position of the tube on the inclined plane is known in a transverse vertical plane (i.e. in a vertical plane perpendicular to the tube feed direction, or longitudinal direction), whereby the control unit of the machine is able to determine, on the base of suitable geometrical parameters of the machine, of the tube and of the inclined plane, the exact point where to position a loading tool (which may be either the bending tool normally present on the bending head of the machine or a tool specially designed for this purpose) to take the tube from the inclined plane. The tube is then made available to the bending head in an initial position, for instance the stop position at the bottom of the inclined plane defined by the aforesaid stop members, and is then moved by the bending head directly from this initial position to a final position where it can be clamped by a tube clamp or similar clamping member carried by the machine body. The automatic loading systems for tube bending machines currently available work well with tubes of circular cross-section, but not so well with tubes of non-circular cross-section. In case of tubes of non-circular cross-section, there is in fact the problem of properly orienting the tube relative to the loading tool in order to avoid damages to the tube resulting from the tube being clamped with a wrong orientation between the jaws of the loading tool or between the bending tool and the die. In order to avoid this problem, the automatic loading systems currently available on the market require a specific loading tool which can be oriented manually or a specific loading fixture designed so as to have exactly the same angle as the one existing between the loading tool and the axis of the tube to be loaded, which obviously involves problems in terms of time and costs for setting and mounting.